What is "to be one flesh"

Flesh \Flesh\ (fl[e^]sh), n. [OE. flesch, flesc, AS. fl[=ae]sc; akin to OFries. fl[=a]sk, D. vleesch, OS. fl[=e]sk, OHG. fleisc, G. fleisch, Icel. & Dan. flesk lard, bacon, pork, Sw. fl["a]sk.]

1. The aggregate of the muscles, fat, and other tissues which cover the framework of bones in man and other animals; especially, the muscles.

   Note: In composition it is mainly proteinaceous, but contains in adition a large number of low-molecular-weight subtances, such as creatin, xanthin, hypoxanthin, carnin, etc. It is also rich in potassium phosphate.

2. Animal food, in distinction from vegetable; meat; especially, the body of beasts and birds used as food, as distinguished from fish.

   With roasted flesh, or milk, and wastel bread.
   --Chaucer.

3. The human body, as distinguished from the soul; the corporeal person.

   As if this flesh, which walls about our life, Were brass impregnable.
   --Shak.

4. The human eace; mankind; humanity.

   All flesh had corrupted his way upon the earth.
   --Gen. vi. 12.

5. Human nature:

   1. In a good sense, tenderness of feeling; gentleness.

      There is no flesh in man's obdurate heart.
      --Cowper.

   2. In a bad sense, tendency to transient or physical pleasure; desire for sensual gratification; carnality.

   3. (Theol.) The character under the influence of animal propensities or selfish passions; the soul unmoved by spiritual influences.

6. Kindred; stock; race.

   He is our brother and our flesh.
   --Gen. xxxvii. 2

7. 7. The soft, pulpy substance of fruit; also, that part of a root, fruit, and the like, which is fit to be eaten.

   Note: Flesh is often used adjectively or self-explaining compounds; as, flesh broth or flesh-broth; flesh brush or fleshbrush; flesh tint or flesh-tint; flesh wound.

   After the flesh, after the manner of man; in a gross or earthly manner. ``Ye judge after the flesh.''
   --John viii. 15.

   An arm of flesh, human strength or aid.

   Flesh and blood. See under Blood.

   Flesh broth, broth made by boiling flesh in water.

   Flesh fly (Zo["o]l.), one of several species of flies whose larv[ae] or maggots feed upon flesh, as the bluebottle fly; -- called also meat fly, carrion fly, and blowfly. See Blowly.

   Flesh meat, animal food.
   --Swift.

   Flesh side, the side of a skin or hide which was next to the flesh; -- opposed to grain side.

   Flesh tint (Painting), a color used in painting to imitate the hue of the living body.

   Flesh worm (Zo["o]l.), any insect larva of a flesh fly. See Flesh fly (above).

   Proud flesh. See under Proud.

   To be one flesh, to be closely united as in marriage; to become as one person.
   --Gen. ii. 24.